Radio frequency power amplifier module

ABSTRACT

An object of the present invention is to provide a radio frequency power amplifier of multi stage amplifying method that is designed to reduce instability of output power caused by electromagnetic coupling of bias supply terminals and interconnections of each stage to thereby operate stably. Another object of the present invention is to provide a radio frequency power amplifier that is designed to reduce distortion of output power caused by electromagnetic coupling of bias supply terminals and interconnections of each stage to thereby provide high efficiency. The above objects can be achieved by providing a first interconnection connected to a terminal for supplying a voltage for collector driving to a power amplifying transistor, a second interconnection connected to a terminal for supplying a voltage for collector driving to a second transistor controlling a base bias voltage of the above transistor, and one or more ground parts for electromagnetic shield, wherein the first interconnection and the second interconnection are separated by one or more of the ground parts for electromagnetic shield.

This application is a Continuation application of U.S. application Ser.No. 11/003,480 filed Dec. 6, 2004, which is a Continuation applicationof U.S. application Ser. No. 10/822,781 filed Apr. 13, 2004, which is aContinuation application of U.S. application Ser. No. 10/315,144 filedDec. 10, 2002. Priority is claimed based on U.S. application Ser. No.11/003,480 filed Dec. 6, 2004, which claims priority to U.S. applicationSer. No. 10/822,781 filed Apr. 13, 2004, which claims priority to U.S.application Ser. No. 10/315,144 filed Dec. 10, 2002, which claimspriority to Japanese Patent Application Nos. 2002-217789 and 2001-379960filed on Jul. 26, 2002 and Dec. 13, 2001, respectively, all of which isincorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a radio frequency power amplifier usedin cellular phone handset, and more particularly to a voltage powersupply method of reducing mutual interference between circuits through apower supply line.

2. Description of the Prior Art

Recently, there has been an increasing demand for cellular phone handsetas typified by cellular phones to be more compact in size and lighter inweight, and therefore research and development is being vigorously madeto satisfy the demand. Conventional power amplifying circuits fortransmission used in cellular phone handset require negative voltagepower supply or negative voltage power creation circuit, have many partconfigurations, and cannot therefore meet the demand of being compact insize and light in weight. Accordingly, heterojunction bipolartransistors of Gallium Arsenide compound semiconductor (hereinaftersimply referred to as GaAsHBT) are expected as amplifying devices usedin radio frequency power amplifiers for transmission because they arecapable of single positive voltage power supply and have excellent radiofrequency characteristics.

FIG. 12 shows a conventional radio frequency power amplifier employingGaAsHBT, disclosed in Japanese Patent Laid-Open No. H10-75130. The radiofrequency power amplifier comprises: an input impedance matching circuit401; a power amplifying transistor 410; an output impedance matchingcircuit 402; and a base bias voltage control circuit 403 for the poweramplifying transistor 410. The base bias voltage control circuit 403comprises a transistor 411 and resistors 420 and 421. The referencenumeral 430 denotes power supply for driving the collectors of thetransistors 410 and 411, and the reference numeral 431 denotes powersupply for controlling the gain of the radio frequency power amplifier,which is applied to the base of the power amplifying transistor throughthe base bias voltage control circuit. The base bias voltage controlcircuit, by substantially supplying a base current Ibb of the poweramplifying transistor from the power supply for collector driving, isgenerally used to reduce a current Iapc for gain control to be suppliedfrom the power supply for gain control and thereby reduce current supplycapacity demanded to external control circuits to generate a voltage forgain control.

With saturation amplifiers complying with the GSM (Global System forMobile Communication) system widely used principally in Europepresently, a trade-off relationship between output power and power addedefficiency is a major problem in the development of radio frequencypower amplifiers.

Moreover, with linear amplifiers complying with the W-CDMA (WidebandCode Division Multiple Access) system, which is one of third generationmobile communication systems, in addition to the trade-off betweenoutput power and power added efficiency, a trade-off relationship existsbetween distortion and power added efficiency, as described in page 36in “Electronic Technology June, 2000” published by Nikkan Kogyo Shinbun.

Therefore, in the linear amplifiers, reduction in distortion leads to anincrease in power added efficiency of radio frequency power amplifiers,which, in turn, leads to an increase in the performance of the radiofrequency power .amplifiers.

SUMMARY OF THE INVENTION

In the above conventional radio frequency power amplifier, the powersupply for driving the collector of the transistor making up the basebias voltage control circuit is shared with the power supply for drivingthe collector of the power amplifying transistor. The above conventionalradio frequency power amplifier has no capacitor enough to cut off ahigh frequency leakage signal of the collector current Icc due to outputpower of the power amplifying transistor, e.g., capacitor enough tocouple a collector line and the ground. Consequently, the high frequencyleakage signal of the collector current Icc is fed back to the basecurrent Ibb of the power amplifying transistor through the base biasvoltage control circuit, causing the radio frequency power amplifier tooperate unstably.

Moreover, the high frequency leakage signal of the collector current Iccis fed back to the base current Ibb of the power amplifying transistorthrough the base bias voltage control circuit, causing an increase indistortion in the output power of the radio frequency power amplifier.

An object of the present invention is to provide a radio frequency poweramplifier of multi stage amplifying method that is designed to reduceinstability of output power caused by electromagnetic coupling of biassupply terminals and inter lines of each stage to thereby operatestably. Another object of the present invention is to provide a radiofrequency power amplifier of multi stage amplifying method that isdesigned to reduce distortion of output power caused by electromagneticcoupling of bias supply terminals and inter lines of each stage tothereby provide high efficiency characteristics.

The above objects can be achieved by providing the radio frequency poweramplifier of the claims 1 to 7 with the first terminal for supplying avoltage for collector driving to the first transistor for poweramplification, the second terminal for supplying a voltage for collectordriving to a second transistor controlling a base bias voltage of thefirst transistor, the first interconnection for connecting the firstterminal and the collector of the first transistor, the secondinterconnection for connecting the second terminal and the collector ofthe second transistor, and one or more ground parts for electromagneticshield, wherein the first terminal and the second terminal are separatedby one or more of the ground parts for electromagnetic shield, and thefirst interconnection and the second interconnection are separated byone or more of the ground parts for electromagnetic shield.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit diagram of a radio frequency power amplifier moduleimplementing first and second embodiments of the present invention;

FIG. 2 is a diagram of substrate layer configuration in the firstembodiment of the present invention;

FIG. 3 is a schematic diagram of a front-side conductive layer in thefirst embodiment of the present invention;

FIG. 4 is a schematic diagram of a back-side conductive layer in thefirst embodiment of the present invention;

FIG. 5 is a perspective view of major portions in the first embodimentof the present invention;

FIG. 6 is a diagram showing a relationship between the width of a groundpart for electromagnetic shield and inter-circuit isolation in anembodiment of the present invention;

FIG. 7 is a schematic diagram of substrate layer configuration in thesecond embodiment of the present invention;

FIG. 8 is a schematic diagram of a front-side conductive layer in thesecond embodiment of the present invention;

FIG. 9 is a schematic diagram of a first inner conductive layer in thesecond embodiment of the present invention;

FIG. 10 is a schematic diagram of a second inner conductive layer in thesecond embodiment of the present invention;

FIG. 11 is a perspective view of major portions in the second embodimentof the present invention;

FIG. 12 is a circuit diagram of a conventional radio frequency poweramplifier;

FIG. 13 is a perspective view of major portions of a radio frequencypower amplifier of the present invention; and

FIG. 14 is a diagram showing actual measurement values of output voltagedistortion of a linear amplifier.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, the present invention will be described in more detail,using preferred embodiments. The accompanying drawings are used in thedescription to ease understanding of the present invention.

<First Embodiment>

FIG. 1 shows a configuration of a radio frequency power amplifiercircuit in a first embodiment. The radio frequency power amplifiercircuit comprises: an input impedance matching circuit 1; an input stagetransistor 10 for power amplification; an inter-stage impedance matchingcircuit 2; an output stage transistor 11 for power amplifier; an outputimpedance matching circuit 3; and a base bias voltage control circuit 20for transistors 10 and 11, wherein the base bias voltage control circuit20 in this circuit comprises the transistors 12 and 13 and resistors 30and 31. The radio frequency power amplifier circuit comprises: a firstterminal 40 for supplying a voltage for collector driving to the outputstage transistor 11; a second terminal 41 for supplying a voltage forcollector driving to the transistors 12 and 13 making up the base biasvoltage control circuit 20; a third terminal 42 for supplying a currentand a voltage for gain control to the transistors 12 and 13 making upthe base bias voltage control circuit 20; a signal input terminal 43 forinputting a signal to the base of the input stage transistor 10; asignal output terminal 44 for extracting a signal from the collector ofthe output stage transistor 11 through the output impedance matchingcircuit 3; a first interconnection 50 for connecting the first terminal40 and the collector of the output stage transistor 11 through theoutput impedance matching circuit 3; a second interconnection 60 forconnecting the second terminal 41 and the collectors of the transistors11 and 12 making up the base bias voltage control circuit; and a groundmetal side (hereinafter referred to as a ground part for electromagneticshield) 70. Furthermore, the first terminal 40 and the second terminal41 are separated from each other by one or more of the ground part 70for electromagnetic shield, and the first interconnection 50 and thesecond interconnection 60 are also separated from each other by one ormore of the ground part 70 for electromagnetic shield. The ground part70 for electromagnetic shield comprises a conductive film and is formedon a dielectric plate, for example, by a metal evaporating method orsputtering method. It may also be formed by coating a dielectricmaterial on a dielectric plate. A material such as metal may be used.

FIG. 2 shows a configuration of a module (substrate layer) embodying thecircuit of FIG. 1. The substrate comprises a front-side conductive layer200; a back-side conductive layer 201; and a dielectric plate 100. Theconductive layers are primarily made of, e.g., copper and gold, and thedielectric plate is primarily made of, e.g., ceramic and resin.

FIG. 3 shows a schematic diagram of the front-side conductive layer 200,FIG. 4 shows a schematic diagram of the back-side conductive layer 201,and FIG. 5 shows a perspective view of major portions.

In FIG. 3, the reference numeral 1 denotes the input impedance matchingcircuit; 2, the inter-stage impedance matching circuit; 3, the outputimpedance matching circuit; 10, the input stage transistor; 11, theoutput stage transistor; 20, the base bias voltage control circuit ofthe power amplifying transistors 10 and 11; 12 and 13, transistorsmaking up the base bias voltage control circuit; 30 and 31, resistors ofthe base bias voltage control circuit; 50, the first interconnection;60, the second interconnection; 110, a first ground part forelectromagnetic shield separating the first interconnection 50 and thesecond interconnection 60; 100, a dielectric plate; and 101 a to 101 f,through holes connecting the conductive layers as shown in FIG. 5.

The power amplifying transistors 10 and 11, and the base bias voltagecontrol circuit 20 are formed on an identical or discrete semiconductordevice, and mounted on the front-side conductive layer. Particularly,the power amplifying transistors 10 and 11 are formed on a semiconductordevice primarily made of GaAs.

In FIG. 4, 40 denotes the first terminal; 41, the second terminal; 42,the third terminal; 43, the signal input terminal; 44, the signal outputterminal; and 120, a second ground part for electromagnetic shieldseparating the first terminal 40 and the second terminal 41.

In FIG. 5, 520 denotes a semiconductor device mounting the base biasvoltage control circuit 20.

The present invention has a module structure as shown in FIGS. 3 to 5.Hereinafter, embodiments of the module configuration will be described.The base of the input stage transistor 10 is connected to the signalinput terminal 43 through the input impedance matching circuit 1 and athrough hole 101 e. The collector of the output stage transistor 11 isconnected to the signal output terminal 44 through the output impedancematching circuit 3 and a through hole 101 f, and connected to the firstterminal 40 through the output impedance matching circuit 3, the firstinterconnection 50, and a through hole 101 d. The bases of thetransistors 12 and 13 making up the base bias voltage control circuitare connected to the third terminal 42 through a through hole 101 a. Thecollectors of the transistors 12 and 13 are connected to the secondterminal 41 through the second interconnection 60 and a through hole 101b. The first ground part 110 for electromagnetic shield is connected tothe second ground part 120 for electromagnetic shield through one ormore through hole(s) 101 c, and the second ground part 120 forelectromagnetic shield is grounded on a motherboard.

The operation of a first embodiment of the radio frequency poweramplifier of the present invention will be described using the drawings.

In FIG. 1, a signal inputted from the signal input terminal 43 isextracted from the signal output terminal 44 through the input impedancematching circuit 1, the input stage transistor 10, the inter-stageimpedance matching circuit 2, the output stage transistor 11, and theoutput impedance matching circuit 3. The base bias voltage controlcircuit 20, by substantially supplying base currents Ibb1 and Ibb2 ofthe power amplifying transistors 10 and 11 from a collector current Icc3from the second terminal 41, is used to reduce a current Iapc for gaincontrol to be supplied from the power supply for gain control andthereby reduce current supply capacity demanded to external controlcircuits to generate a voltage for gain control. For example, by usingthe transistor 12 to drive the base of the input stage transistor 10, areduction amount of the current Iapc for gain control to be suppliedfrom the power supply for gain control is substantially inverselyproportional to an amplification rate of the transistor 12 for basedriving. Since a current amplification rate of transistors is normally10 or more, a current required can be reduced at least one tenth incomparison with cases where the transistor 12 for base driving is notused. As a result, at least 90 percent or more of the current Ibb1 fordriving the base of the first stage transistor for power amplificationcan be obtained by amplifying the collector current Icc. This is alsotrue for the operation of the transistor 13 for driving the base of theoutput stage transistor 11.

In FIGS. 1, 5, and 11, the ground parts 70, 110, 130, and 140 forelectromagnetic shield are grounded to the second ground part 120 forelectromagnetic shield through one or more through hole(s), and thesecond ground part 120 for electromagnetic shield is grounded to themotherboard or the like. Because of this construction, all the groundparts 70-110, 120, 130, and 140 for electromagnetic shield become zerovoltage. Assume that the radio frequency power amplifier of the presentinvention is activated at a frequency of 900 MHz with a power supplyvoltage of 3.5 V, and output power of the output stage transistor 11 is35 dBm. At this time, voltage amplitude in the collector of the outputstage transistor 11 becomes about 15 V, and current and voltage of thefirst interconnection 50 leak due to influence of the high frequencyoutput power. Normally, for the power supply line formed on themotherboard or the like so as to electrically connect to the powersupply for collector driving and the first and second terminals mountedon the module, a capacitive device of several μF is inserted between thepower supply line and the ground so that the high frequency leakagesignal does not propagate to the power supply for collector driving orother power supply lines.

However, the substrate is small in size, and a capacitive device isgenerally placed between the line for supplying a voltage for drivingthe collectors of the input stage transistor 10 and the output stagetransistor 11 that are formed on the module, and the ground to minimizeinfluence of the line for supplying a voltage for driving the collectorson a high frequency circuit system (not shown). However, the capacitivedevice of several μF used for the motherboard or the like is large inpart size and difficult to use, and actually has a capacity of equal toor less than 100 nF. Accordingly, high frequency leakage signals ofcurrent and voltage of the first interconnection 50 propagate to thebase bias voltage control circuit 20 through the second interconnection60.

FIG. 6 shows results of three dimensional electromagnetic simulationwhen an alumina ceramic substrate is used as a dielectric plate. FIG. 6shows a relationship between the width of the first ground part (orground metal side) 110 for electromagnetic shield inserted between thefirst interconnection 50 and the second interconnection 60, andisolation values between the first interconnection 50 and the secondinterconnection 60.

In the above simulation, the interval between the first interconnection50 and the first ground part 110 for electromagnetic shield, and theinterval between the second interconnection 60 and the first ground part110 for electromagnetic shield are fixed to 0.1 mm, a minimum dimensiongenerally used to fabricate high frequency modules.

It is understood from FIG. 6 that, when the first ground part forelectromagnetic shield is absent, an isolation value is about −30 dB,which is insufficient for the output voltage 35 dBm. Accordingly, asdescribed in the operation of the base bias voltage control circuit,since the base current Ibb2 of the output stage transistor 11 issubstantially supplied from the collector current Icc3 of the fourthtransistor 13 through the second interconnection 60 from the secondterminal 41, a high frequency leakage signal generated in the secondinterconnection 60 propagates to the base current Ibb2 of the outputstage transistor 11. When the base current suffers a high frequencyleakage signal, the transistor generally becomes unstable in operation,so that the operation of the radio frequency power amplifier becomesunstable.

However, the radio frequency power amplifier, as described above, isprovided with the first terminal 40 and first interconnection 50 forsupplying a voltage for collector driving to the output stage transistorfor power amplification, and the second terminal 41 and secondinterconnection 60 for supplying voltages for collector driving to thetransistors 12 and 13 making up the base bias voltage control circuit,and further includes the first ground part 110 for electromagneticshield provided between the first interconnection 50 and the secondinterconnection 60, and the second ground part 120 for electromagneticshield provided between the first interconnection 40 and the secondinterconnection 41. By forming the first ground part 110 forelectromagnetic shield and the second ground part 120 forelectromagnetic shield so that their width is 0.2 mm or more, anisolation value of −50 dB or less can be obtained.

With this construction, since the current and voltage high frequencyleakage signals neither propagate from the first interconnection 50 tothe second interconnection 60 nor from the first terminal 40 to thesecond terminal 41, the base currents Ibb1 and Ibb2 of the poweramplifying transistors 10 and 11 making up the radio frequency poweramplifier are stabilized and the operation of the power amplifyingtransistors 10 and 11 is stabilized, so that the above problem can besolved.

<Second Embodiment>

Hereinafter, a second embodiment of the present invention will bedescribed using the drawings. The circuit configuration of a radiofrequency power amplifier in a second embodiment is the same as that inFIG. 1 used in the first embodiment.

FIG. 7 shows the configuration of a module (substrate layer) in thesecond embodiment. The substrate comprises: a front-side conductivelayer 300; a first inner conductive layer 301; a second inner conductivelayer 302; a back-side conductive layer 303; and dielectric plates 100a, 100 b, and 100 c. Components of the conductive layers and thedielectric plates are the same as those in the first embodiment.

FIG. 8 shows a schematic diagram of the front-side conductive layer 300,FIG. 9 shows a schematic diagram of the first inner conductive layer301, FIG. 10 shows a schematic diagram of the second inner conductivelayer 302, and FIG. 11 shows a perspective view of major portions. Inthe second embodiment, a schematic diagram of the back-side conductivelayer 303 is the same as that in FIG. 4 used in the first embodiment.

In FIG. 8, the structures of an input impedance matching circuit 1,input stage transistor 10 for power amplification, inter-stage impedancematching circuit 2, output stage transistor 11 for power amplifier,output impedance matching circuit 3, base bias voltage control circuit20, and transistors 12 and 13 and resistors 30 and 31 making up the basebias voltage control circuit 20 are the same as those in the firstembodiment.

FIG. 9 shows a schematic diagram of the inner conductive layer 301 ofFIG. 7. The reference numeral 130 denotes a third ground part forelectromagnetic shield.

In FIG. 10, the reference numeral 50 denotes the first interconnectionand 140 denotes a fourth ground part for electromagnetic shield.

As shown in FIGS. 8 to 11, the base of the input stage transistor 10 isconnected to the signal input terminal 43 through the input impedancematching circuit 1 and the through hole 101 i, and the collector of theoutput stage transistor 11 is connected to the signal output terminal 44through the output impedance matching circuit 3 and the through hole 101j.

At the same time, the collector of the output stage transistor 11 isconnected to the first terminal 40 through a through hole 101 k forconnecting the output impedance matching circuit 3, the front-sideconductive layer 300, and the second inner conductive layer 302, and athrough hole 101 m for connecting the first interconnection 50 formed onthe second inner conductive layer 302, the second inner conductive layer302, and the back-side conductive layer 303. The bases of thetransistors 12 and 13 making up the base bias voltage control circuitare connected to the third terminal through a through hole 101 g, andthe collectors of the transistors 12 and 13 are connected to the secondterminal 41 through a through hole 101 h for connecting the secondinterconnection 60, the front-side conductive layer 300, and theback-side conductive layer 303.

The third and fourth ground parts 130 and 140 for electromagnetic shieldare connected to the second ground part 120 for electromagnetic shieldformed on the back-side conductive layer 303 through one or more throughhole(s) 101 l, and the second ground part 120 for electromagnetic shieldis grounded to the motherboard or the like.

The third ground part 130 for electromagnetic shield has a width equalto or greater than W1+2×W2, where W1 is the width of the firstinterconnection 50 and W2 is dielectric plate thickness.

This is a result derived from the three dimensional electromagneticsimulation, based on the fact that the intensity of electromagneticfield to the third ground part for electromagnetic shield from the firstinterconnection is the strongest within an angle of 45 degrees from theend of the first interconnection and becomes weaker for greater angles.

The radio frequency power amplifier of the present invention shown inthe second embodiment has the first inner conductive layer 301comprising mainly the third ground part for electromagnetic shieldbetween conductive layers having the first interconnection 50 and thesecond interconnection 60, respectively.

Although, in the second embodiment, the first interconnection 50 isformed on the second inner conductive layer 302 and the secondinterconnection 60 is formed on the front-side conductive layer 300, thefirst interconnection 50 may be formed on the front-side conductivelayer 300 and the second interconnection 60 may be formed on the secondinner conductive layer 302.

The first interconnection 50 and the second interconnection 60 mayextend to plural conductive layers. An example of this is describedusing FIGS. 7 and 13.

In FIG. 13, the reference numeral 40 denotes a first terminal formed onthe back-side conductive layer 303 (see FIG. 7); 50-a, part of the firstinterconnection 50 formed on the second inner conductive layer 302;50-b, part of the first interconnection 50 formed on the front-sideconductive layer 300; 101 m, a through hole for connecting the firstterminal 40 and the first interconnection 50-a; 101 n, a through holefor connecting the first interconnection 50-a and the firstinterconnection 50-b; 41, a second terminal formed on the back-sideconductive layer 303; 60, a second interconnection formed on thefront-side conductive layer; and 101 h, a through hole for connectingthe second terminal 41 and the second interconnection 60. The firstground part 110 for electromagnetic shield is formed between the firstinterconnection 50-b and the second interconnection 60. The third groundpart 130 for electromagnetic shield formed on the first inner conductivelayer 301 is disposed between the first interconnection 50-a and thesecond interconnection 60. In the second inner conductive layer, thefourth ground part 140 for electromagnetic shield is formed between thefirst interconnection 50-a and the through hole 101 h. In this way, themethods of the first and second embodiments may be mixed as required.

Although, in the second embodiment, the input impedance matching circuit1, the inter-stage impedance matching circuit 2, and the outputimpedance matching circuit 3 are formed on the front-side conductivelayer 300, they may be formed dispersedly on the front-side conductivelayer 300 and the second inner conductive layer 302.

The operation of the present invention in the second embodiment is thesame as that in the first embodiment.

Although, in the first and second embodiments, a back-side electrodesystem of fabricating terminals on a back-side conductive layer isadopted, a side electrode system of fabricating the terminals at thesides of a substrate may be adopted. Although, in the first and secondembodiments, two-stage amplifiers are used, one-stage amplifiers orthree-or-more stage amplifiers may be used.

In the first and second embodiments, the second terminal 41 is shared asa terminal for supplying a voltage for collector driving to thetransistors 12 and 13 making up the base bias voltage control circuitand a terminal for supplying a voltage for collector driving to thepower amplifying transistor 10. However, the second terminal 41 may beformed separately to a fourth terminal for supplying a voltage forcollector driving to the transistors 12 and 13 making up the base biasvoltage control circuit and a fifth terminal for supplying a voltage forcollector driving to the power amplifying transistor 10.

Although, in the first and second embodiments, the transistors making upthe power amplifying circuit use GaAsHBT, it goes without saying thatthe present invention is not limited to this substance and numerousvariations may be used. For example, HBT using SiGe (silicon germanium)and HBT using InP (indium phosphide) are applicable.

Although, in the first and second embodiments, the transistors making upthe power amplifying circuit are bipolar transistors, the presentinvention is not limited to the bipolar transistors. For example, MOSFET(field-effect transistors) is applicable as the above transistors. Inthis case, although the above circuit operation is different for currentdriven types and voltage driven types, a radio frequency power amplifieroperating stably, which is an object of the present invention, can beobtained.

Although, in the first and second embodiments, emitter follower is usedas the circuit form of the base bias voltage control circuit 20, thepresent invention is not limited to this form, and any forms such assource follower and voltage follower using an operational amplifier maybe employed.

In the first and second embodiments, a ground part for electromagneticshield is disposed between the first interconnection 50 connecting thecollector of the transistor 11 and the first terminal 40 for supplying avoltage for collector driving to the transistor 11 through the outputimpedance matching circuit 3, and the second interconnection 60connecting the collectors of the transistors 12 and 13 and the secondterminal 41 for supplying a voltage for collector driving to thetransistors 12 and 13.

In FIG. 11, the ground parts 130 and 140 for electromagnetic shield aregrounded to the second ground part 120 for electromagnetic shieldthrough one or more through hole(s), and the second ground part 120 forelectromagnetic shield is grounded to the motherboard or the like.Because of this construction, all the ground parts 120, 130, and 140 forelectromagnetic shield become zero voltage. Assume that the radiofrequency power amplifier of the present invention is activated at afrequency of 900 MHz with a power supply voltage of 3.5 V, and outputpower of the output stage transistor 11 is 35 dBm.

At this time, voltage amplitude in the collector of the output stagetransistor 11 becomes about 15 V, and current and voltage of the firstinterconnection 50 leak due to influence of the high frequency outputpower. Normally, for the power supply line formed on the motherboard orthe like so as to electrically connect to the power supply for collectordriving and the first and second terminals mounted on the module, acapacitive device of several μF is inserted between the power supplyline and the ground so that the high frequency leakage signal does notpropagate to the power supply for collector driving or other powersupply lines.

However, as described as to the operation of the first and secondembodiments, an object of the present invention is to preventpropagation of an electromagnetic leakage signal from the firstinterconnection 50 supplying a voltage for collector driving to thepower amplifying transistor 11 to the input side of the transistor 11and thereby stabilize output power of the power amplifier.

Accordingly, it is desirable that ground parts for electromagneticshield are disposed not only between the first interconnection 50 andthe second interconnection 60, but also between the firstinterconnection 50 and a third interconnection (not shown) connectingthe base of the transistor 10 and the emitter of the transistor 12,between the first interconnection 50 and a fourth interconnection (notshown) connecting the base of the transistor 11 and the emitter of thetransistor 13, and between the first interconnection 50 and a fifthinterconnection (not shown) connecting the collector of the transistor10 and the second terminal 41, respectively.

FIG. 14 shows actual measurement values of ±5 MHz adjacent channelleakage power ratio in a state in which a capacitive device is insertedbetween the first interconnection 50 and the fourth interconnection andthere is electromagnetic interaction between the first interconnectionand the fourth interconnection, and in a state in which a ground partfor electromagnetic shield is inserted between the first interconnectionand the fourth interconnection and there is no electromagneticinteraction between the first interconnection and the fourthinterconnection. The adjacent channel leakage power ratio is generallyused as a parameter indicating the distortion of output power of a poweramplifier to input power. Measurement conditions are room temperature,W-CDMA modulation signal input, input signal frequency 1.95 GHz, andoutput power 27 dBm.

It is understood from FIG. 14 that distortion is reduced by about 15 dbby inserting a ground part for electromagnetic shield between the firstinterconnection and the fourth interconnection. Accordingly, applyingthe radio frequency power amplifier of the first and second embodimentsto a linear amplifier reduces an adjacent channel leakage power ratio.

Although W-CDMA modulation is exemplified in the above embodiment, itgoes without saying that the same effects can also be obtained inapplication to radio frequency power amplifiers used in modulationsystems requiring linear amplifiers such as general CDMA modulation,EDGE (Enhanced Data-rate for GSM Evolution), PDC (Personal DigitalCellular) and OFDM (Orthogonal Frequency Division Multiplexing).

According to the present invention, high frequency leakage signals incurrents and voltages of a power supply line for driving in a radiofrequency power amplifier are suppressed and the operation of the radiofrequency power amplifier can be stabilized. Moreover, if the radiofrequency power amplifier of the present invention is applied to alinear amplifier, the distortion of output power to input power can bereduced with the effect that the efficiency of the radio frequency poweramplifier can be increased.

1. A radio frequency power amplifier module comprising: a firsttransistor to amplify a signal inputted through an input or inter-stageimpedance matching circuit and output a first amplified signal, disposedat the first input stage; a second transistor to amplify the firstamplified signal inputted through an output terminal of said firsttransistor and output a second amplified signal, disposed at the lastoutput stage: a first terminal to supply a driving voltage to an outputterminal of said second transistor; a first interconnection to couplesaid first terminal and the output terminal of said second transistor; asecond terminal to supply current to an input terminal of said firsttransistor; a second interconnection to couple said second terminal andthe input terminal of said first transistor; and a first ground part forelectromagnetic shield being provided between said first terminal andsecond terminal.
 2. The radio frequency power amplifier module accordingto claim 1, further comprising: a dielectric plate; a first ground partfor electromagnetic shield provided on a back side of said dielectricplate; a first through hole, provided on said dielectric plate, forelectrically connecting said first terminal and a first interconnection;and a second through hole, provided on said dielectric plate forelectrically connecting said second terminal and said secondinterconnection; wherein each of said first and second interconnectionscomprises a conductive layer mounted on a main front side of saiddielectric plate, and wherein said first ground part comprises aconductive layer provided in an area in which said first and secondinterconnections are not in contact with each other.
 3. The radiofrequency power amplifier module according to claim 2, wherein saidfirst ground part for electromagnetic shield has a width of 0.2 mm ormore.
 4. The radio frequency power amplifier module according to claim1, wherein at least one of said first, and second transistors is aheterojunction bipolar transistor of Gallium Arsenide, SiliconGermanium, or Indium Phosphide.
 5. A radio frequency power amplifiermodule comprising: a first transistor to amplify a signal inputtedthrough an input or inter-stage impedance matching circuit and output afirst amplified signal, disposed at the first input stage; a secondtransistor to amplify the first amplified signal inputted through anoutput terminal of said first transistor and output a second amplifiedsignal, disposed at the last output stage; a third transistor to drivethe first transistor; a first terminal to supply a driving voltage to anoutput terminal of said second transistor; a first interconnection tocouple said first terminal and the output terminal of said secondtransistor; a second terminal to supply current to an input terminal ofsaid first transistor; a second interconnection to couple said secondterminal and the input terminal of said first transistor; a firstthrough hole, provided for electrically connecting said secondinterconnection and second terminal; a second through hole, provided forelectrically connecting said first interconnection and the outputterminal of said second transistor; and a first ground part forelectromagnetic shield being provided between said first through holeand said second through hole.
 6. The radio frequency power amplifiermodule according to claim 5, further comprising: a first dielectriclayer having a first surface on which said first interconnection isformed; a second dielectric layer having a first surface on which saidsecond interconnection is formed; a third dielectric layer disposedbetween said first and second dielectric layers; said first ground partfor electromagnetic shield formed on a first surface of said thirddielectric layer; a second ground part for electromagnetic shield isformed on a first surface of said first dielectric layer; a third groundpart for electromagnetic shield is formed on a second surface of saidfirst dielectric layer; said first and second through hole, provided onsaid first dielectric layer, said second dielectric layer, and saidthird dielectric layer; and a third through hole, provided on said firstdielectric layer, for electrically connecting said third ground part forelectromagnetic shield and said first ground part for electromagneticshield; wherein each of said first and second interconnections comprisesa conductive layer mounted on a main front side of said first dielectricplate and said second dielectric plate respectively, and wherein saidfirst ground part comprises a conductive layer provided in an area inwhich said first and second through holes are not in contact with eachother.
 7. The radio frequency power amplifier module according to claim6, wherein said first ground part for electromagnetic shield has a widthof 0.2 mm or more.
 8. The radio frequency power amplifier moduleaccording to claim 5, wherein at least one of said first, and secondtransistors is a heterojunction bipolar transistor of Gallium Arsenide,Silicon Germanium, or Indium Phosphide.
 9. A radio frequency poweramplifier module comprising: a first transistor to amplify a signalinputted through an input or inter-stage impedance matching circuit andoutput a first amplified signal, disposed at the first input stage; asecond transistor to amplify the first amplified signal inputted throughan output terminal of said first transistor and output a secondamplified signal, disposed at the last output stage; a third transistorto drive the first transistor; a first terminal to supply a drivingvoltage to an output terminal of said second transistor; a firstinterconnection to couple said first terminal and the output terminal ofsaid second transistor; a second terminal to supply current to an inputterminal of said first transistor; a second interconnection to couplesaid second terminal and the input terminal of said first transistor; afirst through hole, provided for electrically connecting said secondinterconnection and second terminal; a second through hole, provided forelectrically connecting said first interconnection and said firstterminal; and a first ground part for electromagnetic shield beingprovided between said first through hole and said first interconnection.10. The radio frequency power amplifier module according to claim 9,further comprising: a first dielectric layer having a first surface onwhich said first interconnection is formed; a second dielectric layerhaving a first surface on which said second interconnection is formed; athird dielectric layer disposed between said first and second dielectriclayers; said first ground part for electromagnetic shield is formed on afirst surface of said first dielectric layer; a second ground part forelectromagnetic shield is formed on a second surface of said firstdielectric layer; said first and second through hole, provided on saidfirst dielectric lager, said second dielectric layer, and said thirddielectric layer; and a third through hole, provided on said firstdielectric layer, for electrically connecting said first ground part forelectromagnetic shield and said second ground part for electromagneticshield; wherein each of said first and second interconnections comprisesa conductive layer mounted on a main front side of said first dielectricplate and said second dielectric plate respectively, and wherein saidfirst ground part comprises a conductive layer provided in an area inwhich said first through hole and said first interconnection are not incontact with each other.
 11. The radio frequency power amplifier moduleaccording to claim 10, wherein said second ground part forelectromagnetic shield has a width of 0.2 mm or more.
 12. The radiofrequency power amplifier module according to claim 9, wherein at leastone of said first, and second transistors is a heterojunction bipolartransistor of Gallium Arsenide, Silicon Germanium, or Indium Phosphide.